Fabrication of interweaving hierarchical fibrous composite (iHFC) membranes for high-flux and robust direct contact membrane distillation

Abstract

The industrialization of membrane distillation (MD) is hindered by lack of desirable membranes with high performance. Recently, the engineered electrospun nanofibrous membranes (ENMs), such as dual- or multi-layered ENMs, have displayed superior permeations in MD compared with traditional membranes. However, it is still far from satisfactory due to membrane delamination and performance loss after long-term operation. Herein, inspired by the structure of nest with interweaved branches, we fabricated the interweaving hierarchical fibrous composite (iHFC) membrane comprising the interconnected poly(vinylidene fluoride-co-hexafluoropropylene) (PH) nanofibers and polyethylene terephthalate (PET) microfibers via convectional electrospinning. The hydrophobic PH nanofibers provide an enhanced anti-wetting property and high salt rejection. The PET microfibers could significantly both lower the resistance of mass transfer and improve the heat insulation. Results show that the optimized iHFC membrane having the ratio of PH/PET 1.5/0.8 and membrane thickness 80 μm exhibits both high permeation flux of 65 LMH and stable high performance over 60 h when operated at 40 °C temperature difference. Moreover, the interweaving structure endows the iHFC membrane great mechanical strength and excellent long-term stability. It is believed that the strategy explored, and the unique membrane developed here could pave a path to boost the industrialization of MD membranes.